block: improve logic around when to sort a plug list
Only do it if we have requests for multiple queues in the same
plug.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5f4b93f..2a1a653 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1677,7 +1677,8 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
list_splice_init(&plug->mq_list, &list);
plug->rq_count = 0;
- list_sort(NULL, &list, plug_rq_cmp);
+ if (plug->rq_count > 2 && plug->multiple_queues)
+ list_sort(NULL, &list, plug_rq_cmp);
this_q = NULL;
this_hctx = NULL;
@@ -1866,6 +1867,20 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
}
}
+static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
+{
+ list_add_tail(&rq->queuelist, &plug->mq_list);
+ plug->rq_count++;
+ if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
+ struct request *tmp;
+
+ tmp = list_first_entry(&plug->mq_list, struct request,
+ queuelist);
+ if (tmp->q != rq->q)
+ plug->multiple_queues = true;
+ }
+}
+
static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
{
const int is_sync = op_is_sync(bio->bi_opf);
@@ -1932,8 +1947,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
trace_block_plug(q);
}
- list_add_tail(&rq->queuelist, &plug->mq_list);
- plug->rq_count++;
+ blk_add_rq_to_plug(plug, rq);
} else if (plug && !blk_queue_nomerges(q)) {
blk_mq_bio_to_request(rq, bio);
@@ -1950,8 +1964,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
list_del_init(&same_queue_rq->queuelist);
plug->rq_count--;
}
- list_add_tail(&rq->queuelist, &plug->mq_list);
- plug->rq_count++;
+ blk_add_rq_to_plug(plug, rq);
blk_mq_put_ctx(data.ctx);
